Metal buildings having metal roofing have become popular for commercial, industrial and warehousing uses. These buildings often require roof openings for skylights, fans, air conditioning units and the like. The installation of such equipment requires a roof curb for support.
Traditionally, roof curbs have been designed specifically and custom made to provide a relatively horizontal mounting structure for a particular rooftop appliance given the shape and pitch of a particular roof. Designing and building these traditional roof curbs, often formed from a singular piece of metal to uniquely accommodate a particular roof pitch, has been a laborious and time consuming task for roof curb manufacturers and rooftop appliance installers. Further, because these roof curbs are installed in a metal roof system, the actual opening may vary with respect to the roof corrugations, seams or ribs, which may be ascertainable only shortly before installation. This untimely design-and-build practice delays appliance installation.
Manufacturers developed standardized roof curbs to help limit installation delays. See, for example, U.S. Pat. No. 4,559,753, issued Dec. 24, 1985, to Ralph H. Brueske, for Method of Installing a Prefabricated Curb Unit to a Standing Seam Roof, which describes a method of installing a metal roof curb in which the rims of the curbs are pre-welded to a roof panel, and the curb containing-panel is attached to a large opening cut into the roof. However, this method requires cutting a hole in the roof that is larger than the opening for the equipment that may be susceptible to leakage.
Prefabricated roof curbs tend to be quite large, thus have been difficult to ship in a cost effective and timely fashion, let alone by traditional rapid delivery methods. Consequently, roof curb manufacturers have had to ship their products by truck, which is slower and more expensive.
Traditional roof curbs include four coated steel curb walls positioned to define an open rectangular frame joined by factory welding at the corners. Because welding burns off the corrosion resistant coating of the steel, the manufacturer or installer must provide an additional coating of rust inhibitor paint to keep the roof curb from rusting when installed on the roof. Routine rust inhibitor paint coatings are required to protect the roof curb throughout the life of the product. Mechanical attachment, such as with threaded fasteners, may secure the corners without welding. However, on-site sizing and drilling of traditional roof curb panels creates exposure to corrosive weathering.
What is needed is a standardized, corrosion-resistant roof curb that can be shipped in a disassembled state, which an installer may assemble, size, locate and configure to provide an appropriate roof slope on any roof without welding.